Anode frame



Feb. 3, 1959 D. M. BUCHANAN ANODE FRAME Filed Sept. 23. 1954 N A m H. CN U B N m V A D 1 JT H U i e S s tefl ANODE FRAME David M. Buchanan,Woodside, N. Y., assignor to Union Carbide Corporation, a corporation ofNew York Application September 23, 1954, Serial No. 457,933

1 Claim. (Cl. 204-295) The present invention relates to an improvedanode frame for use in the electrowinning of metal values from anelectrolytic solution.

Prior to the present invention, in compartment type cells employed inthe electrolytic production of chromium, manganese, and other similarmetals, wood was extensively used as an anode frame material to maintainthe anode plate terminals mechanically spaced and electrically insulatedfrom one another, while providing low resistance to the passage ofelectrolyte between and around the anode frames. Difliculty wasencountered in the electrolytic operation because electrolyte absorbedby the wooden anode frame material caused to frame to warp, and in manyinstances, reacted chemically with it. As a consequence, criticaldimensions and clearances could not be maintained for any sustainedlength of time, and steady, eflicient operation of the compartment cellcould not be assured.

Attempts were made in the past to solve this problem by using as anodeframe materials, resinous materials having chemical resistance toelectrolytic solutions. But none of these had any signal success. Forinstance, polyethylene and related resins proved to be too elastic, anddid not possess sufiicient structural rigidity. Other resins such asmelamines and ureas showed evidences of chemical attack by theelectrolyte. Still other resins like fluorothene were impracticalbecause of high cost.

It is, therefore, an object of the present invention to provide an anodeframe made from resinous materials having good dimensional stability athigher temperatures normally encountered in electrolytic platingoperations, and resistance to chemical attack by solutions used in theelectrowinning of metals.

Another object of the invention is to provide an anode frame that can bemade by injection molding in one piece from a resinous material havinghigh dielectric properties and chemical resistance to electrolytesolutions used for the electrowinning of metals.

In the drawings:

Fig. 1 is a front elevational view with parts broken away, and partly insection, illustrating an anode frame constructed in accordance with thepresent invention;

Fig. 2 is a side elevational view of the anode frame shown in Fig. 1;

Fig. 3 is a plan view of the anode frame shown in i Fig. 1;

Fig. 4 is an enlarged vertical section taken along the line 4-4 in Fig.1;

Fig. 5 is a cross-sectional view of the anode frame taken along .theline 5-5 in Fig. 1;

Fig. 6 is a cross-sectional view of the anode frame taken along the line6-6 in Fig. 1; and

Fig. 7 is an anode frame similar to Fig. 1, but showing modificationthereof.

The present invention is an improvement upon prior an anode framematerials. It has been found that a very suitable anode frame to be usedin electrolytic having a styrene-acrylonitrile copolymer base.

2,872,406 Patented Feb. 3, 1959 processes can be produced from anorganic compound Preferably those organic compounds are employed whichcontain between percent and percent of acrylonitrile. At thetemperatures employed in normal electrolytic plating operations thesematerials are unaffected by dilute acids and alkalies. They possessexcellent electrical insulation properties, outstanding surface finish,and good moldability properties. In addition, anode frames made 0 ofstyrene acrylonitrile copolymer material are particu- July well suitedto be mass produced by injection molding, and may be cured tack-free inthe presence of air in the range to be encountered in the practice ofthe invention.

The preferred class of compounds within the practice 'of the presentinvention are copolymers made by reacting together approximately 28parts of acrylonitrile and 72 parts styrene monomer. They arecopolymerized to form a thermoplastic copolymer which can be moldedunder heat and pressure. It is characterized by having a higher heatdistortion temperature and greater toughness than polystyrene, andgreater resistance to reagents, such as electrolytes, than polystyreneand other thermoplastics.

One of the advantages arising from the use of anode frames made ofcompounds of the type mentioned above overthe the use of wooden anodeframes is the fact that in the temperature range normally employed inelectrolytic plating operations, clearance dimensions can be more easilycontrolled. In the practice of the present invention the composition ofthe organic compound to be used as the anode frame material can beeasily and carefully controlled in exactly the correct proportions toachieve the optimum value for any specific type of electrolyte which isto be used in conjunction therewith.

In forming the anode frame material, several variables will affect thequality of the product. One of the more important variables is thetemperature. While electrolytic plating will usually occur at relativelylow temperatures, in practice the temperature employed will normally beon the order of F. to 180 F., and

preferably about F. However, it is to be understood that temperatures-up to about 200 F. may be safely employed in plating operations. Abovetemperatures of about 200 F., distortion is quite rapid, makingsubsequent use of the anode frame impractical.

The anode frame of the present invention may be constructed to complywith the specifications of most elec trolytic processes, and isparticularly well suited for use in the electrowinning of metals such aschromium and manganese, which are adapted to deposit out of aqueouselectrolytic solutions. The electrode frame of the present invention isnot affected by electrolytes having a chloride or a sulfate radical attemperatures below 200 F. Further, such frame may be efliciently andeffectively operated at a pH of between 1.8 and 2.6.

In accordance with the present invention, an anode frame 10 ispreferably made from an acrylonitrile copolymer material of the typedescribed hereinabove. This frame may comprise a top wall 12, a bottomwall 13 and side walls 14 and 15, which may be suitably molded in onepiece, as by injection molding. In order to impart structural rigidityto the anode frame. 10, each of these anode frame walls may be channelshaped, the top Wall 12 being preferably U-shaped and having a web 17and upwardly projecting flanges 18 and 19.

For the purpose of receivably carrying an anode plate terminal 20, theweb 17 is provided with an elongated slot 21, the slot 21 extending fromjuncture of web 17 with the web of side wall 14 to juncture of web 17with web of side wall 15. In the modification shown in Fig.

7, two anode plate receiving slots 22 and 23 are illustrated in orderthat the anode frame assembly may be operated at full or one-half ratedcapacity or to facilitate handling of the anode plates.

The bottom anode frame wall 13' is also of channel form, preferablyhaving an inverted U-shaped cross secare of U-shaped channel form, eachhaving respectively a web 29 and opposed and outwardly extending flanges3t). Vertically spaced ribs 32 in each of the side walls 14 and serve toimpart strength and rigidity to the anode frame.

To confine the anolyte solution within the immediate vicinity of theanode plate, a gas permeable, liquid semipermeable, flexible cloth ormembrane covering 33, preferably of Dynel woven fabric, is cemented toboth sides of the anode frame 10. This construction permits escape ofthe gases evolved at the positive plates, and at the same time restrictsflow of anolyte solution outside the confines of the anode frame.

Where a series of anode frames are used in an electrolytic process, bothfaces of each of the anode frames are covered with a membrane covering33 in the manner illustrated in Fig. 1. However, where the anode frameis disposed at the extreme end of the frame series, only one facethereof need be covered with said membrane covering. in such case theendmost face is usually sealed with a liquid and gas-impermeable sheetof material, preferably of the same composition as the anode frame.

In the embodiment of the invention shown in Fig. 1, the anolyte isintroduced into an opening 34 in the top of the anode frame 10 by meansof an anode frame feed tube 35, preferably made of anelectrolyte-resistant material similar to that of the anode frame 10.Circulation of the anolyte solution in the frame 10 is effected by apiping arrangement (not shown) which communicates with the inside of theframe 10 through inlet and outlet openings 36 and 37 in the side wall29.

Bafiles may be provided if necessary inside the anode frame to preventthe anolyte from being discharged directly through the discharge opening37.

It will be noted that because of the flexibility of the membrane 33, itmay contact the anode plate and disrupt the uniformity of the platingoperation. -To the end that contact between the membrane 33 and theanode plate 20 may be avoided, there is provided therebetween a seriesof anode frame rods 38. In assembly, these rods are held in position attheir upper and lower ends respectively by means of openings 39 in theupper web 17 (see Fig. 4), which straddle the slot 21, and vertically 6aligned blind end sockets 40 in the lower web 24 positioned on oppositesides of the guide slot 27.

The thickness of the side webs 29, as well as the flanges of the anodeframes, may be suitably tapered to facilitate ejection of the anodeframe from the mold.

From the above it will be seen that an improved anode frame may be madein one piece as by injection molding from a styrene acrylonitrilecopolymer organic compound. The anode frame is admirably suited for usein most electrolytic plating processes, being not only resistant tochemical attack, but also exhibiting remarkable dimensional stability attemperatures up to 200 F.

it will be understood that modifications and variations may be effectedwithout departing from the scope of the novel concepts of the presentinvention.

What is claimed is:

An anodic electrolytic cell adapted to be removably inserted in a frameunit of a cell tank with other like cells without swelling comprising amonolithic, hollow, rectangular frame of a styrene acrylonitrilecopolymer base having chemical resistance to electrolytic solutions andhigh structural rigidity and dimensional stability at temperatures up toapproximately 200 C., said frame comprising a pair of spaced verticalside walls, a lower wall integral with the lower ends of said sidewalls, and an upper wall integral with the upper ends of said sidewalls, said frame walls forming a pair of flat rectangular surfaces inparallel planes, a pair of liquid semi-permeable diaphragm coveringsattached respectively to said surfaces and forming an enclosedcompartment in the interior of said frame, an elongated slot in saidupper wall adapted to loosely receive a fiat rectangular electrode, apair of openings in one of said side walls for circulating liquidelectrolyte in said compartment, each of said frame walls comprising acentral web and a pair of outwardly projecting end flanges, the innersurface of said web forming a part of the inside wall surface of saidenclosed compartment, and the outer opposed surfaces of said projectingflanges forming a part of said flat rectangular surfaces, and aplurality of spaced rigid rods secured in said frame and disposed onopposite sides of said compartment for preventing contact between saiddiaphragm coverings and said electrode, whereby warpage and deterioration of said cell in an electrolyte solution is substantiallyavoided.

References Cited in the file of this patent UNITED STATES PATENTS1,368,227 Sperry Feb. 8, 1921 1,861,796 Hodges June 7, 1932 2,512,973Schumacher June 27, 1950 2,543,059 Rawles Feb. 27, 1951 2,739,116Carosella Mar. 20, 1956 FOREIGN PATENTS 543,294 Great Britain Feb. 18,1942 OTHER REFERENCES Bureau of Mines Bulletin #463, 1946, pages to 66including Figs. 30, 31 and 33.

Schildknecht, Vinyl and Related Polymers, 1952, pages 48 to 54.

